Chapter 8 Breast Cancer Treatment-Related Imaging and the Postoperative Breast
This chapter provides an overview of clinically driven breast cancer evaluation; the sequence of events after a breast cancer diagnosis; locoregional breast cancer treatment options, including sentinel lymph node (SLN) biopsy; the normal postoperative breast; postradiation therapy change; ipsilateral breast tumor recurrence (IBTR) after lumpectomy; and the appearance of the breast after mastectomy with or without reconstruction.
Palpable or image-detected breast abnormalities constitute the majority of consultations for breast specialists. After assessment, the specialist usually orders a complete imaging workup of suspicious findings and may ask for a fine-needle aspiration (FNA) or percutaneous core biopsy if the findings are worrisome enough. If results of percutaneous biopsy are indeterminate or discordant, or if the patient prefers, a diagnosis may be established by open surgical breast biopsy.
No matter how breast cancer is diagnosed, follow-up treatment depends on the tumor size and stage. If the tumor is large, women may undergo neoadjuvant chemotherapy (i.e., chemotherapy given before excision of the primary tumor). Neoadjuvant chemotherapy shrinks the tumor and allows the medical oncologist to determine the chemotherapy’s effectiveness in vivo. If the tumor shrinks to a small enough size, the woman may undergo breast-conserving therapy and radiation therapy, rather than mastectomy.
If the breast cancer is small, surgical management is almost always recommended initially to remove the cancer. Lumpectomy (almost always followed by breast radiotherapy) and mastectomy are the two principal options for local therapy. Survival is the same with either approach. Of the two, lumpectomy (also referred to as breast-conserving surgery, partial mastectomy, or quadrantectomy) is more commonly preferred. Mastectomy may be performed in a variety of fashions, such as using skin-sparing techniques, and can be performed with or without breast reconstruction.
At the time of surgery, SLN biopsy commonly accompanies removal of the primary tumor to determine if axillary lymph nodes harbor metastases. A full axillary node dissection (levels I and II are commonly performed today) follows if the sentinel node harbors anything more than isolated tumor cells (AJCC Staging Manual).
Whole-breast radiotherapy usually is performed after lumpectomy to eliminate microscopic residual disease remaining in the breast. The purpose of radiotherapy is to suppress tumor recurrence in the remaining breast parenchyma in general and in the tissue around the lumpectomy cavity in particular. This typically involves 6 weeks of whole-breast radiotherapy with an electron beam boost dose to further eradicate any residual cells near the surgical margins. Clinical studies evaluating radiotherapy doses delivered over shorter time periods are now under way and include hypofractionated schedules (e.g., treatment delivered over approximately 3 weeks) and accelerated partial-breast irradiation (APBI), in which the radiotherapy period ranges from 5 days to a single dose given at the time of lumpectomy. If successful, these new radiotherapy approaches will allow much shorter radiotherapy treatment periods for most women.
It is important to understand how patients progress from workup to cancer diagnosis and through treatment and how surgery, radiation, and systemic therapy, affect imaging of the treated breast. This chapter details each of these steps.
Combined Clinical and Imaging Workup of Breast Abnormalities
Once the referring physician finds a suspicious breast mass or receives a suspicious mammographic report, the patient undergoes a thorough history and a focused breast examination. Usually a breast cancer specialist (commonly a general surgeon with an interest in breast cancer, a dedicated breast surgeon, or a surgical oncologist) then estimates the patient’s risk of having breast cancer, seeks patterns of familial breast cancer, and helps the patient to make an informed decision about imaging versus immediate intervention.
Most patients are then referred for a thorough diagnostic imaging workup. Patients with suspicious palpable abnormalities undergo ultrasound, with or without mammography, depending on age, family history, and level of concern over the finding. For example, ultrasound would likely be the sole imaging modality in an 18-year-old woman with a new breast lump and no family history of breast cancer. On the other hand, ultrasound and mammography would likely be used for a 25-year-old woman with a new palpable lesion and an extensive family history of breast cancer in young relatives. The final decision as to whether or not to incorporate mammography into a very young patient’s workup is a shared responsibility of the clinician directing the breast workup, the radiologist performing the initial imaging (ultrasound in this case), and the patient. Breast magnetic resonance imaging (MRI) is used sparingly during the initial evaluation of a palpable finding, unless there is an extensive family history, in which case it serves a dual role as both a diagnostic tool on the affected breast and a screening tool on the contralateral breast.
For patients with nonpalpable findings on screening mammography, workup always includes diagnostic mammography. For suspicious calcifications alone, the radiologist usually obtains magnification mammograms, often not needing ultrasound. An exception might be extensive pleomorphic microcalcifications, in which ultrasound might be used to search for masses within the area that could be indicative of invasive cancer, prompting biopsy. However, if there is an image-detected mass, area of architectural distortion, or palpable mass, the radiologist usually uses both mammography and ultrasound to evaluate the abnormality, estimate its size, and direct later biopsy. Breast MRI may be valuable in selected cases, as discussed in Chapter 7. Ideally, the radiologist correlates all physical and imaging findings in the report to form a composite picture of all potential abnormalities and their level of suspicion on mammography, ultrasound, and MRI.
Using the combined report, the directing clinician and radiologist plan percutaneous or open biopsy to sample all areas of concern. This sequence varies from patient to patient. This may be as simple as FNA in a young woman with a single area of fibrocystic nodularity and a normal ultrasound or as complex as numerous core biopsies or surgical biopsies in one or both breasts using palpation or image guidance for localization.
Although there are no hard and fast rules about what defines a “suspicious” palpable abnormality, in general cancers are firm or hard, asymmetric compared with the opposite breast, irregular in shape, and feel as if they are rising up out of the breast tissue, rather than spreading out in the substance of the breast. Physical examination, ultrasound/mammography, and FNA are generally considered the “minimum” intervention for a suspicious palpable finding and in combination are referred to as the triple test. For suspicious palpable findings in which all components of the triple test are negative, the risk of malignancy is considered approximately 3% or less. Even if all components of the triple test are normal, it is extremely important to inform the patient that there is a low, but measurable, false-negative rate for the triple test and that surgical excision can be performed to completely exclude the possibility of malignancy. This discussion is ideally documented in the medical record. Patients with likely benign palpable findings, unremarkable imaging, and normal percutaneous sampling with FNA (i.e., a negative triple test) usually undergo a single follow-up visit 3 to 6 months later with the referring physician. Patients who undergo image-guided core biopsy usually undergo repeat imaging 6, 12, and 24 months later to assess stability of any residual findings. Progressive findings on repeat palpation or breast imaging at follow-up prompt surgical excision.
For suspicious image-detected nonpalpable lesions, image-guided FNA, percutaneous core biopsy, or wire-localized excisional biopsy is generally considered the “minimum” intervention. Percutaneous needle core biopsy has become the more common choice. Here, too, it is important to inform the patient of the limitations of percutaneous core biopsy—specifically, that there is a small false-negative rate with needle biopsy. Wire-localized surgical biopsy is usually recommended to exclude malignancy if percutaneous biopsy is indeterminate or discordant with imaging findings. For an anxious patient, wire-localized surgical excision may be a better option initially; the surgeon will usually document this discussion in the medical record, too. For some patients with lesions close to the chest wall or nipple, wire-localized excisional biopsy may also be the safer initial approach.
Breast Cancer Diagnosis and Treatment
When a combined clinical and imaging workup leads to a breast cancer diagnosis, treatment planning usually involves a consideration of surgery, chemotherapy, and radiation therapy, with the goal to remove all the cancer from the breast, optimize chances for locoregional control, and eradicate occult foci of metastatic disease via systemic treatment (e.g., hormone therapy, chemotherapy), if indicated. The team of breast imagers, surgeons, medical oncologists, pathologists, radiation oncologists, and breast reconstruction surgeons plan the sequence in which surgery, chemotherapy, and radiation occurs. The pathology report is a key component on which treatment is based. The report states tumor histology; size; estrogen, progesterone, and her2neu receptor status; and lymph node involvement. Traditionally, breast tumors are staged using the TNM (tumor, lymph node, metastasis) Classification on Breast Cancer from the American Joint Committee on Cancer (currently in the 7th edition) (Table 8-1). The treatment plan is based on this classification. A clinical decision algorithm is also available from the National Comprehensive Cancer Network regarding the full spectrum of care; Adjuvant! Online is an Internet-based tool that provides guidance regarding prognosis and the potential benefit of different chemotherapy protocols. Additional tests based on tumor gene signatures are emerging (OncoType DX and MammaPrint) and are the subject of two large randomized trials, one in the United States and the other in Europe. Gene expression profiling may play an increasingly important role in the future; preliminary data suggest improvement in separating high- and low-risk patients.
Locoregional control of the cancer means that the patient undergoes surgical removal of the cancer with a margin of normal breast tissue. (Although the definition of an acceptable margin varies from institution to institution, the more commonly followed models range from simple nontransection [tumor not on inked margin] to 2 mm of normal tissue at the margin.) The patient achieves this locoregional control by either breast-conserving surgery, usually followed by whole-breast irradiation, or mastectomy. As shown by Protocol B-06 conducted by the National Surgical Adjuvant Breast and Bowel Project (NSABP), both approaches yield equivalent local control and identical survival rates in women with tumors 4 cm or smaller in diameter whether the axillary lymph nodes are positive or negative for metastatic disease.
The radiologist helps the team select candidates for breast-conserving surgery or mastectomy by estimating the location and extent of disease. The critical information the surgeon requests relates to lesion location and size. This allows the surgeon to form a three-dimensional (3-D) representation of normal versus malignant tissue, develop a mental image of the tumor within the breast, estimate the amount of additional tissue needed to obtain tumor-free margins, and plan the incision (surgical approach) with the goal of maximizing probability of tumor removal while preserving cosmesis as best as possible. For example, it is difficult to remove an extensive ductal carcinoma in situ (DCIS) completely with microscopically clear margins, and these patients are usually treated with mastectomy. Increasingly, there is interest (though no good randomized data to support) in removing multiple lesions from the same breast while preserving the breast. Multifocal disease refers to lesions in the same quadrant; multicentric disease refers to lesions in separate quadrants. As a straightforward example, a 3-mm satellite lesion is almost always amenable to resection with a primary lesion using breast-conserving techniques with an acceptable cosmetic outcome. In contradistinction, a pair of 3- to 4-cm lesions on opposite sides of the breast are usually treated with mastectomy. There are no hard and fast rules for excising multiple lesions with breast conservation, and excellent clinical judgment must be used. For this reason, in the setting of multiple lesions, the surgeon requests information regarding the number and size of the lesions, as well as their geographic relationship to each other. If too many foci of invasive cancer or extensive DCIS are present, the patient is not a candidate for breast-conserving surgery because the surgeon would have a hard time excising all the cancer and because of concern over an elevated risk of IBTR.
In general, surgeons perform mastectomy when the entire cancer cannot be excised with a good cosmetic result (as just discussed), if the woman has a contraindication to radiotherapy, or if it is the patient’s desire. Usually, patients are offered ipsilateral breast reconstruction with an autologous tissue flap or a tissue expander after mastectomy, unless there is a medical contraindication to reconstruction (e.g., multiple co-morbidities). Because the contralateral breast is often larger than the reconstructed breast, patients may also need reduction mammoplasty on the contralateral side. Characteristic appearances of reduction mammoplasty and breast reconstruction are discussed in Chapter 9.
If the patient has breast-conserving surgery, she usually undergoes postsurgical whole-breast irradiation to achieve control of residual microscopic disease. Relative contraindications to radiation therapy include pregnancy, previous radiation therapy, and collagen vascular disease (Box 8-1). Axillary nodal involvement is not a contraindication. Six randomized trials of lumpectomy and radiation therapy showed that the frequency of local recurrence and overall survival rates are generally comparable to mastectomy. However, IBTRs are reported in 5% of patients at 5 years and in 10% to 15% at 10 years after completion of therapy. Treatment failures (i.e., IBTR) usually undergo salvage mastectomy.
Box 8-1 Contraindications to Whole-Breast Radiation Therapy
Invasive IBTR usually occurs in the lumpectomy site or quadrant within the first 7 years, but rarely earlier than 18 months after treatment. IBTR after 7 years will more likely occur in any quadrant, not necessarily at the original site, and is usually considered a new cancer. IBTR near the original lumpectomy site is associated more frequently with systemic relapse than IBTR in other quadrants, which more often reflect a new primary tumor. IBTR is considered more likely in women who have invasive ductal cancer with an extensive intraductal component, residual disease in the breast, extensive DCIS, lymphatic or vascular invasion, or multicentricity, and is more common in younger women (Box 8-2).
Evaluation of Axillary Lymph Nodes
The treatment of invasive breast cancer has historically involved removal of ipsilateral axillary lymph nodes. This was natural, because most women receiving treatment for breast cancer 100 years ago had nodal involvement. With earlier detection of breast cancer, nodal involvement is no longer the norm. In fact, approximately 65% to 70% of women with newly diagnosed invasive breast cancer have normal lymph nodes and therefore will not derive any benefit from axillary lymph node dissection (ALND).
ALND is also problematic from the standpoint of side effects. It exposes patients to the risk of major complications such as lymphedema, shoulder dysfunction, and sensory changes in and around the axilla. To address this problem, routine level I/level II ALND (Table 8-2) has evolved to use the SLN biopsy as an initial screen for nodal involvement in patients who are clinically node-negative.
|I||Infralateral to lateral edge of the pectoralis minor muscle|
|II||Behind the pectoralis minor muscle|
|III||Between the pectoralis minor and subclavius muscles (Halsted ligament)|
SLN biopsy was initially described for patients with penile cancer, but did not attract much attention until it was broadly adopted for use in melanoma patients. SLN biopsy is performed by injecting a tracer material, either a radionuclide, blue dye, or both into the breast either preoperatively or perioperatively and by looking for evidence of the tracer in one or more sentinel nodes (Box 8-3).
Box 8-3 Sentinel Lymph Node Biopsy Identification Techniques
SLN biopsy alone does not eliminate, but does significantly decrease, the risk of developing the common complications of lymphedema. A level I/level II ALND is now most commonly performed contingent on identification of tumor in one of the sentinel lymph nodes.
The role of the radiologist is to understand the rationale for SLN biopsy and to facilitate its performance. First, the radiologist should not inject tracer into the biopsy cavity or the tumor; tracer injected into a biopsy site cavity is likely to remain in the cavity rather than be transported into the lymphatics. The most common tracers are technetium-99 sulfur colloid and lymphazurin blue; some also use methylene blue dye.
Preoperative lymphoscintigraphy is used in some facilities to assist preoperative localization of sentinel lymph nodes in the axilla or in extra-axillary sites (Fig. 8-1A to C). Most commonly these extra-axillary sites will be in the supraclavicular, infraclavicular, or internal mammary groups. If tracer does not identify an axillary SLN, the surgeon may choose to harvest an SLN from one of these other sites. Some facilities do not remove an internal mammary SLN or other nonaxillary SLN due to the very low frequency of isolated positive biopsies (usually <3%) and the relatively few cases that would result in meaningful changes in prognosis or therapy. Perhaps not surprisingly, institutions that harvest both axillary and internal mammary sentinel lymph nodes have demonstrated a poorer prognosis when lymph nodes at both sites are involved.
Figure 8-1 A to C, Lymphoscintigraphy for sentinel lymph node (SLN) visualization. A, An anterior lymphoscintigram shows activity around the tumor and in the axillary SLN. B, The lymphoscintigram shows radionuclide injected into the biopsy cavity rather than around it; the radiotracer stayed in the biopsy cavity because it could not be transported to the breast lymphatics. C, A lymphoscintigram shows activity in the infraclavicular nodes medial to the tumor site. Note the shielding around the injection site and tumor to improve SLN detection. D to G, Ultrasound to evaluate for lymphadenopathy. D, Ultrasound shows a fine needle aspirating an abnormal lymph node with a very thick cortex that flattened the normal fatty hilum. Aspiration showed breast cancer metastases. E, Ultrasound shows a core biopsy of a low axillary lymph node that has irregular superficial margins. Biopsy showed cancer metastases. Breast cancer that metastasized to the lymph nodes (D and E) on transverse (F) and longitudinal (G) ultrasound. The mass is taller than wide, with microlobulated superficial margins, suspicious for cancer. Invasive ductal cancer was found at biopsy.
Although there are differences of opinion as to the “optimal” location of tracer injection, as well as “optimal” tracer modality, there is general agreement from randomized studies that the technique is sensitive and specific enough to obviate the need for a full ALND in patients whose sentinel nodes test negative for tumor. In general, the SLN is harvested at the time of surgery and tested with touch preparation or frozen section intraoperatively. If there are tumor cells in the SLN, the surgeon proceeds to a completion level I/level II ALND. Nonvisualization of the SLN on lymphoscintigraphy does not preclude SLN identification by the surgeon in the operating room. The SLN may be within thick adipose tissue that can only be identified by the gamma probe in the operating room. The yield for SLN identification in the operating room when it cannot be visualized on lymphoscintigraphy can be increased if blue dye is also used.
Intraoperative evaluation of sentinel lymph nodes occasionally yields false-positive findings. More commonly, false-negative findings occur. This can precipitate return of the patient to the operating room weeks after the original SLN biopsy for completion ALND.
Based on current American Joint Committee on Cancer (AJCC) guidelines, nodal staging is based on the maximal size of the single largest tumor deposit in an SLN (if the SLN is the only involved node) as well as the number of involved lymph nodes. The descriptive category for the smallest extent of disease, isolated tumor cells, means that no single tumor deposit in an axillary node is larger than 0.2 mm. Patients with isolated tumor cells are considered to have normal nodes and are usually not treated with a completion ALND. Proceeding from SLN biopsy alone to the wider axillary node clearance typically requires micrometastatic (>0.2- to 2-mm tumor cell cluster in an SLN) or macrometastatic (>2-mm focus) disease within one SLN. Management of the axilla is performed independent of the decision to pursue lumpectomy or mastectomy.
Not all patients are candidates for SLN biopsy. For example, patients who present with clinically involved axillary nodes usually proceed directly to ALND. However, it is important to exercise caution in declaring an axillary lymph node as clinically positive. With the increased frequency of percutaneous core biopsy, more and more patients are presenting to breast cancer specialists with enlarged “reactive” nodes. A recent study by experienced breast surgeons demonstrated that clinical examination in this setting often overestimates the probability that lymph nodes are involved, which in turn could overestimate the number of patients who proceed directly to ALND. Although SLN biopsy has been widely adopted as a precursor to a full ALND for most patients, many have sought to use imaging studies to obviate the need for SLN biopsy or ALND. Toward this end, investigators have assessed the preoperative appearance of nodes on mammography, ultrasound, MRI, and even positron emission tomography. Among these, only positron emission tomography with a high standardized uptake value may provide near-definitive proof of nodal involvement preoperatively in the absence of percutaneous sampling. Here, too, one must be careful to distinguish between a reactive node versus an uninvolved node.
One preoperative axillary imaging method that has gained a following is axillary lymph node ultrasound with percutaneous FNA of suspicious nodes (see Fig. 8-1D to G). Although this test is not a routine part of the initial breast imaging evaluation, there is a new appreciation for preoperative evaluation of ipsilateral axillary lymph nodes in the setting of breast cancer. Axillary ultrasound is particularly helpful when the results of clinical examination of the axilla are suspicious for cancer. Several studies have recently been published using ultrasound-guided FNA or core biopsy to document nodal involvement preoperatively, thus allowing the surgeon to bypass SLN biopsy. This can obviate several known issues with intraoperative assessment of sentinel lymph nodes, such as the time needed to harvest one or more nodes, the intraoperative time needed for pathology to evaluate the node and, most important, the potential for false-negative touch preparation or frozen section at the time of surgery, which can lead to reoperation at a later date.
Clinical and Breast Imaging Factors in Determining Appropriate Local Therapy: Lumpectomy or Mastectomy
The therapeutic options for local control of a breast malignancy are lumpectomy (almost always followed by radiotherapy) and mastectomy. Lumpectomy (followed by whole-breast radiotherapy) was introduced approximately 40 years ago and offers equivalent survival to mastectomy. Mastectomy has a slightly lower risk of local recurrence than lumpectomy and obviates the need for radiotherapy in most patients. The use of postmastectomy radiotherapy is controversial in premenopausal women with one to three involved nodes (see the meta-analysis of randomized studies with and without radiotherapy by the Early Breast Cancer Trialists’ Collaborative Group, Lancet 2005), but it is a common recommendation for women with tumors larger than 5 cm or with four or more involved nodes. The equivalence in overall survival between lumpectomy with radiotherapy and mastectomy was shown in Protocol B-06 conducted by the NSABP and the Milan I trial conducted in Italy.
The breast imager plays a critical role in aiding the surgeon to make the right therapeutic choice by showing how much cancer is in the breast. There is virtually no disagreement that patients with a unifocal DCIS or invasive cancer may be treated with breast conservation therapy if the entire tumor can be removed with a good cosmetic result and if there are no relative contraindications to radiation therapy (i.e., pregnancy, collagen vascular disease, poorly defined or multicentric disease) or prior radiotherapy involving the breast (Fig. 8-2).
Figure 8-2 Mammography showing a poor candidate for breast conservation. Although this patient felt only one mass in her left breast, craniocaudal (A) and mediolateral oblique (B) mammograms show three spiculated masses over a large region, thus rendering this patient a poor candidate for breast conservation.
The controversy regarding the best surgical approach concerns patients with multifocal disease. Some physicians believe that mastectomy is the proper choice for such patients. This preference may be due to results from the original clinical trials comparing lumpectomy with mastectomy, which involved almost exclusively women with unifocal breast cancers. Hence, the safety of breast conservation with respect to local recurrence, distant metastasis, and survival is not as well documented in women with multifocal disease. Still, surgeons are increasingly offering breast conservation to patients with multifocal disease. Thus, there is no hard and fast rule regarding how many satellite lesions, or what distance between lesions, constitutes an absolute indication for mastectomy. It is the physician’s clinical judgment to avoid predisposing the patient to IBTR; recent data suggest that an IBTR may increase the risk of distant metastasis and death from breast cancer.
Whether the surgeon offers lumpectomy to patients with unifocal disease alone or to patients with multifocal disease, tumor-free margins are a must. For example, offering a woman breast conservation may be reasonable if she has multifocal invasive carcinoma with sub-centimeter lesions 3 mm apart and margins that are tumor-free by several millimeters. On the other hand, breast conservation may not be offered if a patient has multifocal high-grade DCIS scattered over an area of 5 to 6 cm with only a 1-mm margin; in this example, one would be concerned about additional multifocal disease just beyond the surgical margin.
The definition of tumor-free margin varies among institutions, with some accepting the NSABP model of nontransection, and others requiring a 2-mm or greater tumor-free margin. In general, the margin status must be carefully considered in patients with multifocal disease. Ideally, these patients should have the multiple lesions resected in continuity to gain the best histologic understanding of size, extent, and relationship of lesions to one another, and of the true margins.
Proof of multicentric disease has been handled by some surgeons with breast conservation, but the more accepted, and proven, route is with mastectomy as initial treatment. As stated previously, no prospective, randomized study to date has evaluated the safety and effectiveness of breast conservation therapy in the setting of multifocal or multicentric disease. Retrospective studies have been published suggesting that this approach may be safe by demonstrating comparable local recurrence rates in multifocal as well as unifocal disease, whereas others suggest higher IBTR rates. These studies are not powered to draw definitive conclusions but do suggest that such a randomized study in the future may be worthwhile.
Mammography, ultrasound, and MRI for tumor extent are important tools for selecting appropriate breast conservation therapy candidates and planning surgery (Table 8-3). Mammography is the mainstay for determining extent of disease. Mammography identifies diffuse or multicentric disease by finding suspicious breast masses and pleomorphic calcifications. Mammography also can identify benign, extensive, innumerable bilateral calcifications that could hide early tumor recurrence. Such calcifications are a relative contraindication to breast conservation therapy. Furthermore, mammography finds DCIS that is invisible to MRI. Specifically, approximately 25% of DCIS cases are false-negative on MRI and are discovered only by visualizing pleomorphic calcifications on the mammogram.
|Preoperative||Ipsilateral tumor extent and contralateral tumor|
|Establish diagnosis||Percutaneous biopsy|
|Preradiation||Check for residual tumor|
|Postradiation||Baseline/tumor recurrence||Ipsilateral unilateral mammogram (initial one at 6 mo, then every 6–12 mo)|
|Evaluate ipsilateral and contralateral breast||Bilateral mammogram (12 mo)|
MRI, magnetic resonance imaging; SLN, sentinel lymph node; US, ultrasound.
Modified from Dershaw DD: The conservatively treated breast. In Bassett LW, Jackson VP, Fu KL, Fu YS, editors: Diagnosis of diseases of the breast. Philadelphia, 1997, WB Saunders, p. 553.
On the other hand, MRI has been especially useful in predicting tumor extent before the first surgical procedure (Fig. 8-3). Some investigators have claimed particular effectiveness of MRI in women with invasive lobular carcinoma or showing tumor invasion into the pectoralis muscle or chest wall (Fig. 8-4). With respect to invasive lobular carcinoma, several studies have suggested that MRI may be more effective in detecting the extent of disease than physical examination, mammography, and ultrasound. However, false-negative studies in these series have led to mixed opinions regarding the routine use of MRI in staging invasive lobular carcinoma.
Figure 8-3 Magnetic resonance imaging (MRI) showing a poor candidate for breast conservation. A to C, Postcontrast 3-D spectral-spatial excitation magnetization transfer (3DSSMT) MRI slices of the right breast show a mass near the chest wall (arrow; invasive ductal cancer) in part C and adjacent segmental clumped enhancement (arrows) over more than two thirds of the upper left breast in parts A and B, worrisome for ductal carcinoma in situ (DCIS). D and E, In the opposite breast there is linear enhancement (arrows) in the lower breast, also worrisome for DCIS. F, In the extreme medial left breast there is a round, suspicious mass (arrows) that had rapid initial enhancement and late washout on kinetic curves, worrisome for invasive ductal cancer. Biopsies of the outer right breast showed invasive ductal cancer and DCIS (A to C); core biopsy of the left segmental enhancement showed DCIS (D and E) and invasive ductal cancer in the inner left breast mass (F). Because of the widespread cancer in both breasts, the patient is not a candidate for breast conservation.
Figure 8-4 Magnetic resonance imaging (MRI) showing extension into the pectoralis muscle. A, Sagittal, contrast-enhanced, 3-D spectral-spatial excitation magnetization transfer (3DSSMT) MRI shows a spiculated posterior enhancing mass extending into and enhancing the pectoralis muscle. B, MRI showing tumor on top of the pectoralis muscle. In contrast to part A, sagittal, contrast-enhanced, 3DSSMT MRI shows an irregular enhancing mass abutting the pectoralis muscle but without enhancing it, thus suggesting no tumor invasion. Although the surgeon may take some of the pectoralis muscle at surgery to achieve clear margins, the tumor does not extend into the muscle or chest wall.
Chest wall tumor invasion on MRI was shown by obliteration of the fat plane between the tumor and the pectoralis muscle, with muscle enhancement, and was proven in 5 of 5 cases at surgery (Morris et al, 2000). No muscle involvement was seen at surgery when muscle enhancement was absent in 14 of 14 cases.
MRI also helps exclude candidates for APBI when it finds more than one focus of cancer. Bedrosian and colleagues (2003) reported a 95% tumor detection rate with MRI and a change in surgical management in 26% (69/267) of patients requiring wider/separate excision or mastectomy, with pathologic verification in 71% (49/69).
Overall, these studies show that MRI may be helpful in surgical planning, but they also indicate that MRI prompts a number of unnecessary biopsies because of a relative lack of specificity. MRI also has false-negative results in invasive lobular carcinoma and DCIS. Other data show that MRI may be associated with treatment delay and an increased mastectomy rate and does not decrease the number of fewer positive margins at surgery. The use of pretreatment MRI before definitive breast cancer surgery remains controversial, particularly if one anticipates whole-breast radiotherapy. The literature on this subject is extensive.
When imaging is complete, additional dialogue with the breast imaging team or additional review of imaging studies may be necessary to help the surgeon, medical oncologist, or radiation oncologist properly counsel the patient regarding appropriate treatment options. This involves a review of the original workup to ensure that all potential abnormalities on physical examination have been evaluated and that the breast imaging workup has been completed (such as up-to-date contralateral mammography as well as additional ultrasound or mammographic imaging for lesions previously considered of secondary concern). The thorough combination of abnormalities identified by palpation or on breast imaging helps ensure that any suspicious foci of tumor are evaluated and incorporated into the treatment plan.
Normal Postoperative Imaging Changes after Breast Biopsy or Lumpectomy
To perform a local excision for diagnostic or therapeutic purposes, the surgeon makes a skin incision, removes the mass or wire-localized abnormality, and then closes the subcutaneous tissues and skin. More tissue is excised when removing a cancer to obtain a margin of normal tissue. Usually, the surgeon allows the surgical cavity to fill in with fluid and granulation tissue.
As a rule, mammograms are not often obtained immediately after diagnostic surgical excisional biopsy. However, in the rare cases when a mammogram is obtained within a few days of surgery, mammography shows a round or oval mass in the postoperative site representing a seroma or hematoma, with or without air. This mass represents the biopsy cavity, filled with fluid that should resolve over time (Fig. 8-5A and B). The adjacent breast tissue shows thickening of trabeculae in subcutaneous fat and increased density caused by local edema or hemorrhage. Skin thickening at the incision is usually present. On MRI the biopsy site is filled with blood or seroma. The fluid in the biopsy cavity is high signal intensity on T2-weighted noncontrast fat-suppressed images (see Fig 8-5C to E).
Figure 8-5 Normal postbiopsy changes. A, A postbiopsy mediolateral oblique (MLO) view shows a large oval mass representing a huge seroma/hematoma after biopsy for cancer, with two adjacent surgical clips. B, Four years later, the MLO views shows the seroma/hematoma is smaller; the two surgical clips are obscured. C to E, Normal hematoma on magnetic resonance imaging (MRI). C, Precontrast axial nonfat-suppressed T1-weighted MRI shows high signal intensity in the biopsy cavity in the left breast soon after surgery (arrows). D, Precontrast axial fat-suppressed T2-weighted MRI shows high signal intensity in the postbiopsy cavity representing blood and fluid. E, Postcontrast sagittal vibrant MRI shows rim enhancement around the hematoma that contains a small round signal void (air, arrow).
Over the subsequent weeks, the postoperative site resorbs the air and fluid collection; the collection is replaced by fibrosis and scarring, with residual focal skin thickening and breast edema. On MRI the immediate postbiopsy cavity is a fluid-filled structure with surrounding normal healing tissue enhancement for up to 18 months after the biopsy. The biopsy cavity shows high signal intensity, architectural distortion, and a scar that can simulate cancer (Fig. 8-6 and Box 8-4). The biopsy site usually contains fluid from the seroma, which will be bright on T2-weighted images on MRI. Rim enhancement around the biopsy site is normal even if there is no residual tumor and is due to healing. In the ipsilateral axilla, reactive lymph nodes may develop that cannot be distinguished from metastatic disease (Fig. 8-7). MRI after surgery may reveal cancer at the margin edge by showing clumped enhancement or an eccentric residual mass. Although immediate postbiopsy MRI for cancer staging may depict cancer at the biopsy margin, it is more often used to look for cancer elsewhere in the breast away from the biopsy site.
Figure 8-6 Normal postbiopsy changes on magnetic resonance imaging (MRI). A, Postcontrast sagittal 3-D spectral-spatial excitation magnetization transfer (3DSSMT) MRI shows enhancing architectural distortion extending from the skin into the upper breast, representing a normal postbiopsy scar. Note the signal void in the biopsy scar due to methemoglobin (arrow) and skin thickening. B, In another recently postoperative patient treated for cancer, precontrast sagittal fat-suppressed T2-weighted MRI shows high signal intensity fluid in the biopsy cavity, bright fluid in the retroareolar ducts, and thickened skin with subcutaneous thick fluid-filled trabeculae, compatible with breast edema. C, Precontrast sagittal 3DSSMT MRI shows the gray fluid-filled postbiopsy scar. D, Postcontrast sagittal 3DSSMT MRI shows rim enhancement around the dark fluid-filled seroma and associated breast edema. Note that there are no additional masses in this breast to suggest multifocal cancer.
Enhancement on MRI after Biopsy
Up to 9 months after biopsy and radiation therapy, there is strong enhancement in the biopsy site. From 10 to 18 months after therapy, the enhancement slowly subsides, with no significant enhancement in 94% of cases.
From Heywang-Kobrunner SH, Schlegel A, Beck R, et al: Contrast-enhanced MRI of the breast after limited surgery and radiation therapy, J Comput Assist Tomogr 17:891–900, 1993.
Figure 8-7 Postbiopsy changes on magnetic resonance imaging (MRI) with abnormal lymphadenopathy. A, Precontrast axial nonfat-suppressed T1-weighted MRI shows low signal intensity representing fluid in the biopsy cavity soon after surgery. A large lymph node in the left axilla has lost its fatty hilum and is worrisome for metastatic disease. B, Precontrast fat-suppressed sagittal T2-weighted MRI shows the high signal seroma and the lymph node in the left axilla near the chest wall. Note that the lymph node has abnormal low signal intensity, indicating lymphadenopathy. Normal lymph nodes will usually show a thin high signal intensity cortex with a fatty hilum. C, Precontrast sagittal 3-D spectral-spatial excitation magnetization transfer (3DSSMT) MRI shows the seroma and the lymph node in the left axilla. D, Postcontrast sagittal 3DSSMT MRI shows the nonenhancing seroma and the enhancing abnormal lymph node in the left axilla. E, Postbiopsy ultrasound shows the fluid-filled biopsy cavity in the left breast corresponding to the fluid cavity seen on MRI. F, Ultrasound of the abnormal lymph node seen on the MRI shows a thick cortical heterogeneous rim and flattening of the fatty hilum by the abnormal metastatic disease in the lymph node. G, Doppler ultrasound shows marked vascular flow within the lymph node. The usually thick rim, heterogeneity of the cortex, flattening of the fatty hilum, and increased vascular flow are all abnormal findings worrisome for metastatic disease. Biopsy of the lymph node showed metastatic disease.
Normal postoperative findings on mammography include architectural distortion, increased density, and parenchymal scarring in at least 50% of patients (Box 8-5). These findings diminish in severity over time (Fig. 8-8A to I). After 3 to 5 years, the findings should be stable on subsequent mammograms. On the mammogram, in 50% to 55% of cases, the biopsy cavity resolves so completely that it leaves no scar or distortion in the underlying breast parenchyma, and only comparison with prebiopsy mammograms indicates that breast tissue is missing. In other cases, the scar appears as a chronic architectural distortion or a spiculated mass more evident on one projection than the other.
Normal Postoperative Findings for Benign Disease
Increased focal density (edema) near the biopsy site (early)
Oval fluid or fluid/air collection (early)
Complete resolution of biopsy findings (late; 50% to 55% of all cases)
Time when findings resolve: 3 to 5 years after biopsy
Postoperative findings seen after 3 to 5 years (45% to 50% of all cases)
Data from Brenner RJ, Pfaff JM: Mammographic changes after excisional breast biopsy for benign disease, AJR Am J Roentgenol 167:1047–1052, 1996; and Sickles EA, Herzog KA: Mammography of the postsurgical breast, AJR Am J Roentgenol 136:585–588, 1981.
Figure 8-8 A to E, Prebiopsy mammogram and normal postbiopsy changes. Magnified craniocaudal (CC) (A) and mediolateral (B) mammograms show an ill-defined mass with a few calcifications in the outer left breast. C, Ultrasound shows an ill-defined hypoechoic mass in the left breast. Core biopsy showed invasive ductal cancer. Left CC (D) and mediolateral (E) mammograms show a wire through the mass before excisional biopsy. Pathology showed invasive ductal cancer with negative margins. Two years later, postbiopsy CC (F) and mediolateral (G) views show mild architectural distortion, skin deformity, and an ill-defined scar (arrows) below a linear metallic scar marker over the skin where the cancer was removed. Notice skin thickening and architectural distortion in the left axilla from sentinel lymph node dissection. Five years later, postbiopsy CC (H) and mediolateral (I